In the prior art, fluorocarbon rubber was generally vulcanized by three types of vulcanization methods i.e., amine, polyol, and peroxide vulcanization methods. See Honda and Kawauchi, Kogyo Zairyou (Industrial Material), 31 5, page 35 and Goda and Sugimoto, Journal of the Japan Rubber Society, 51, 4, page 209.
As to the vulcanization of silicone rubber, typical vulcanization methods include peroxide vulcanization, condensation vulcanization, and addition vulcanization utilizing hydrosilylation. See Rubber Chemistry and Technology, 52. page 437.
Attempts were recently made to impart low-temperature properties characteristic of silicone rubber to fluorocarbon rubber. To this end, it was proposed to concurrently vulcanize fluorocarbon rubber and silicone rubber using a peroxide vulcanizing agent which is common to both fluorocarbon rubber and silicone rubber. See Kunio Goto, Kogyo Zairyou (Industrial Material), 19. 10, page 34, and Japanese Patent Publication Nos. 5463/1987 and 44107/1986.
However, the prior art peroxide vulcanization had several drawbacks. In the peroxide vulcanization of fluorocarbon rubber, a vulcanization activator such as triallyl isocyanurate and triallyl cyanurate was generally used along with the peroxide vulcanizing agent. When vulcanization was effected by the hot air vulcanization (HAV) method, a vigorous foaming phenomenon occurred, resulting in a spongy rubber product which was commercially unacceptable in view of mechanical strength, dimensional accuracy, and appearance. Since it was difficult to form vulcanized rubber articles of quality and processability by the HAV method, the peroxide vulcanization of fluorocarbon rubber largely depended on high pressure steam vulcanization and hot mold vulcanization methods irrespective of their cost.
Similar problems arose in vulcanizing rubber compositions comprising fluorocarbon rubber and silicon rubber components with peroxides.